A motor can transmit a rotational force of a rotor to a shaft so that the shaft may drive a load. For example, the shaft may be connected to a drum of a washing machine to drive the drum. In some examples, the shaft may be connected to a fan of a refrigerator to drive the fan to supply cold air to a space. As another example, the motor may be used in a compressor to compress refrigerant.
A rotor in a motor can be rotated by an electromagnetic interaction with a stator. In some example, a coil may be wounded around the stator so that the rotor can rotate with respect to the stator as an electric current is applied to the coil.
The stator may include a stator core, and the stator core may be made of a conductor, for instance. In some examples, the stator may include a structure that is fixed to an object such as a motor housing, a motor bracket, or a tub of a washing machine.
FIG. 1 illustrates a conventional 3-phase-4-polarity-6-slot motor according to the related art.
The motor 1 includes a stator 10 and a rotor 20. The rotor 20 is provided in the stator and configured to be rotatable with respect to the stator.
The stator 10 may include a yoke 11, and a plurality of teeth 12 that are projected inwards from the yoke 11. A pole shoe 13 extends from an inner radial end of the teeth 12 in both circumferential directions.
A slot 14 is defined between two teeth in a space where a coil 15 is wounded. The coil 15 is wounded around one of the teeth 12 to fill in both slots 14 located nearby.
The coil 15 is wounded to distinguish u-phase, v-phase and w-phase from each other to apply 3-phase AC to the motor. As one example, u-phase, v-phase and w-phase coils are alternatively wounded around the teeth along a circumferential direction.
A securing hole 16 may be defined in the yoke 11 to secure the stator 10 or the motor 1 to an object. The securing hole 16 may be provided in the outermost area of the yoke 11 in order not to affect the magnetic flux.
The yoke 11 may have a ring shape. In some examples, as shown in FIG. 1, the yoke 11 may have a polygonal shape. In any shapes, the yoke 11 may be continuously formed along a circumferential surface. In these cases, a magnetic body forming the yoke may be provided along the circumferential surface.
The teeth 12 may be provided with the yoke 11. For example, the teeth 12 may be integrally formed with the yoke 11 as one body so that the teeth 12 together with the yoke 11 may be referenced to as a stator core. The stator core before the coil is wounded may have a uni-body structure.
The rotor 20 may include a ring-shaped rotor core 21. A shaft hole 22 may be formed in the center of the rotor core 21. The shaft is insertedly coupled to the shaft hole and the rotation of the rotor may generate the rotation of the shaft.
A plurality of coupling holes 23 may be formed in the rotor core 21 and steel plates are multi-layered via the coupling holes 23 to be coupled to each other.
A permanent magnet 24 may be provided in the rotor core 21. As one example, permanent magnets 24 may be provided in an outer circumferential surface of the rotor core 21 along the circumferential direction. N-poles and S-poles of the permanent magnets 24 may be alternatively magnetized along the circumferential direction. FIG. 1 shows that 4 permanent magnets are magnetized into N-poles and S-poles along the circumferential direction alternatively.
The motor having the permanent magnets provided in the rotor core 210 may include a brushless direct current (BLDC) motor. As the permanent magnets are provided in the rotor core 21, a performance of the motor may be improved, and a control of the motor may be performed precisely.
The motor having the stator type has several points of improvement.
For example, the yoke 11 is provided as the integral part, and the stator core including the teeth 12 and the yoke 11 is also provided as the integral part. In this case, the area of the slot may be small, which may limit the number of coil turns and a diameter of the wound coils. The wire loss generated in the coil is relatively large so that it may be difficult to increase efficiency.
In some cases, the winding work of the coil may be performed using a nozzle. In these cases, the fill factor may decrease, and the winding workability may be deteriorated.
In some cases, it may be difficult to change the external appearance and size of the stator core, which may limit reduction of the material used for fabricating the stator core. For example, the shape or size of the stator core may be changed little in the conventional motor. In this case, it may be difficult to reduce material used for the stator core.